Antistatic synthetic resins and fibers



United States Patent i ANTISTATIC SYNTHETlC RESINS AND FIBERS Shinichi Tomiyama, Ichikawa-shi, Hideo Marnmo, Mu-

sashino-shi, and Makoto Takai, Chiba-shi, Japan, as-

signors to Lion Yushi Kabushiki Kaisha, Edogawa-iru,

Tokyo-to, Japan, a joint-stock company of Japan No Drawing. Filed Nov. 30, 1964, Ser. No. 414,831

14 Claims. (Cl. 26075) This invention relates to a method of suppressing electrostatic charges in synthetic resins and fibers. More specifically, this invention is directed to a method of suppressing electrostatic charges in synthetic resins and fibers normally tending to generate such charges, by incorporating metal salts of ainphoteric surface active agents into the synthetic resins and fibers.

The problem of static electricity in synthetic resins and fibers is very serious and much effort has been devoted to eliminating or reducing the magnitude of accumulated electrostatic charges. The problem is manifested in contamination and dust accumulation on articles made from the synthetic resins and fibers and in annoying shocks and sometimes dangerous sparks from formed articles, textiles and films from the synthetic resins and fibers.

These difficulties arise not only in the service 'life of the formed synthetic resins and fibers compositions, such as sheets, filaments and cast and molded articles, but also during the manufacturing of such articles, which can resuit in a slowdown in production, waste and hazards of explosions.

Articles comprising synthetic resins and fibers tend to accumulate electrostatic charges during manufacture, treatment and use. These accumulated electrostatic charges are troublesome in that not only do they render the articles more difiicult to handle during manufacture and treatment, but also in that they greatly increase the tendency of the finished articles to accumulate unwelcome dust in use.

Many methods have been proposed to prevent the accumulation of static charges, none of which are entirely satisfactory. External methods such as temperature and humidity control, and dipping into aqueous surface active agent solutions have been employed in production operations, but antistatic protection thereby is temporary and exists only when the synthetic resins and fibers are exposed to such condition.

A great number of agents have also been proposed for treating the surface of synthetic resins and fibers t-o prevent the generation or accumulation of electrostatic charges. However, such treatments are generally temporary in nature since these agents are removed by washing, leaching or abrasion.

All surface treatment methods, however, require additional handling of the formed articles from the synthetic resins and fibers during such treatment. This is generally undesirable from a production handling viewpoint and undesirable to the ultimate user if repeated applications are necessary. While such a surface treatment is effective, static protection of the articles is removed with washing or contact with water because of the high Water solubility of the surface active agents.

It is known that internal modification of synthetic resin and fiber compositions may be effective in reducing static accumulation. Such internal modification is generally superior to any surface treatment orcoating because of the permanency achieved, and can be accomplished easily by adding to the synthetic resins and fibers an antistatic agent which is unreactive with and compatible to the synthetic resins and fibers, and is stable up to the high temperatures at which the synthetic resins and fibers are processed.

3,29%,fififi Patented Jan. 17, 1967 ICQ It is, therefore, one of the objects of the present invention to provide a method for suppressing electrostatic accumulation by an antistatic agent which can be incorporated into a resinous composition, thereby eliminating the necessity of repeated separate surface applications to obtain substantial antistatic protection over the service life of the article.

It is a further object of this invention to provide an antistatic agent, which, when incorporated into a resinous composition, will not sweat out or exude to the surface of the composition.

It is still a further object of this invention to provide an antistatic agent for reducing the static gene-rating and accumulating tendency of a wide variety of resinous composition which will not react with the resinous compositions or seriously alter or change the physical properties of the resin blends, when employed in amounts sufiicient to give effective antistatic protection.

According to the present invention, it has been found that electrostatic generating tendencies of synthetic resins and fibers can be suppressed by incorporating metal salts of amphoteric surface active agents into the synthetic resins and fibers. The metal salts of amphoteric surface active agents have been found to give antistatic protection which is substantially permanent for the service life of the articles made from synthetic resins and fibers. It has also been found that these products do not sweat out or exude to the surface of the articles made from synthetic resins and fibers, and are not easily leached out by exposure to water. These metal salts of amphoteric surface active agents may be prepared by various methods in which alkylamines or basic nitrogen compounds are converted into metal salts of amphoteric surface active agents by introduction of anion radicals and salt formation with metal radicals. These metal salts of amphoteric surface active agents are effective in suppressing the accumulation of electrostatic charges when employed in amounts of at least part by weight per hundred parts of the synthetic resins and fibers.

For most applications, amounts of about one half to ten parts by weight per hundred parts of the synthetic resins and fibers are preferred, although a greater amount can be employed. The optimum concentration of antistatic agent is dependent upon such factors as the degree of static elimination desired and the kinds of synthetic resins and fibers to be treated. No undesirable changes in physical properties of the synthetic resins and fibers are noticed when the antistatic agents are employed within these preferred limits.

The antistatic agents of this invention can be incorporated into a wide variety of synthetic resins and fibers normally tending to accumulate electrostatic charges during their service life.

Such synthetic resins and fibers which are susceptible to accumulating static charges in which the antistatic agents are particularly useful include the hydrophobic polymers, copolymers and polycondensates such as polyethylene, polyvinyl chloride, polymethacrylates, polyamides, polyethylene glycol terephthalate, polypropylene polystyrene and the like. Particularly good results are obtained on polyethylene and polypropylene.

The synthetic resins and fibers can, after the incorporation of the antistatic agents, be formed in any desired shape such as sheet, film, filament, or into cast or mold articles.

The synthetic resins and fibers into which these antistatic agents may be incorporated can also contain other materials such as dyes, pigments, fillers, plasticizers, lubricants, and the like without adversely affecting the effectiveness of these antistatic agents. These products can be incorporated into the synthetic resins and fibers during any stage of the preparation of the synthetic resins and fibers themselves, or by mixing into the synthetic resin and fiber blends before the forming operation.

These metal salts of amphoteric surface active agents have the following chemical formulas:

N-CHz N-CHE wherein R represents a radical selected from a group consisting of alkyl radicals containing 7 to 21 carbon atoms; X is a material selected from a group consisting of CH fo R1 in wherein n is an integer of from 1 to 6, m an integer of from 1 to 7, y is selected from a group consisting of alkylene radical containing 2 to 6 carbon atoms and R and R are selected from a group consisting of H, alkyl radical containing 1 to carbon atoms, hydroxyalkyl radical, alkylaryl radical, and CH COO, at least one of said R and R being CH COO;

M is material selected from a group consisting of H, Mg, Ca, Cd, Sn, Ba, Pb, Al, Fe, Co, Ni, Cu, Zn and Mn and including no H along; and x and y are numbers which are determined by valency of said M and number of anions in [[1] of the above Formula 1.

Metal salts described above and in the examples which follow are prepared by a method in which higher alkyl imidazolines or their derivatives in which the alkyl groups contain at least 7 carbon atoms are reacted with monochloroacetic acid or its sodium salt, and the resulting sodium salts are then converted to desired metal salts by double decomposition.

Example 1 100 parts of low density polyethylene and 1 part of a metal salt of amphoteric surface activator having the following chemical formula were placed in a Banbury Mixer and blended in a normal way.

The pellet obtained from the above mixture was fed to an extrusion machine and was extruded in a sheet form of 1 mm. thick at a die temperature of 200 C. After aging the sheet at a relative humidity of 65 percent and a constant temperature of C., the electric resistance of the sheet was measured at the same conditions. Also, the sheet was rubbed with clean Nylon Taffeta and the static electricity generated was measured by a variable capacitance electrostatic voltmeter. In comparison with Blank Test, the static charge and the surface resistance were remarkably lowered thereby indicating satisfactory antistatic protection. The results are shown in the following Tables I, 2 and 3.

TABLE 1 N-CI-Iz CHzCOO CHzCHzOH 2 Antistatie Surface Volume Agent N 0. R M Resistivity Resistivity (SI-em.)

17 Blank Tcst NCH2 All CHzC H2O H a Antistatre Surface Volume Agent N 0 R Resistivity Resistivity (9) (rt-em.)

TABLE 3 NCH2 R-C\ NC Hz M HO C 112 O O CIIzCHzOII Static Generation Antistatic (Volts) Autistutic R M Agent in- Ageut N o. corpoi'ated (Percent) Rubbed Rubbed 300 times 900 times 1. 0 280 870 1. 0 320 920 1.0 70 200 0. 2 950 l, 500 7 C17II Can 1.0 120 280 2. 0 5 30 Blank Test 3, 500 4, 500

Example 2 The procedure of Example 1 was repeated with the exception that 1 part of a metal salt of amphoteric surface activator synthesized from l-aminoethyl-Z undecylimidazoline and monochloroacetic acid was incorporated into parts of low density polyethylene. The results are presented in Tables 4 and 5 below.

TABLE 4 N--CH2 CuH C /NCH2 M HO CHQCH2N(CH2COO)2 CIIQC'OOII Antistatic Surface Volume Agent No. M Resistivity Resistivity (Q) (SI-c111.)

1.8 10 72x10 5.3 10 4.8)(10 2.9X10 1.J l 5.4)( 513x10 1.9)(10 5.3)(10 1.4 1(J 11BX10" TABLE 0 N-CH2 CnH2aC N-CH2 A12 110 CH2GH2N(CI-I2CII2COO)2 CH2OOOH a Surface Volume Antistatic Agent No. Resistivity (Q) Resistivity 24 2.1Xl0 1.2)(10 Blank Test 1.4)(10 1.6)(10 Example 3 1 part of different antistatic agents from among Nos. 7, 8, 9 and 15 was blended with 100 parts of polystyrene pellets same as Example 1 and then the mixture was extruded in a sheet form of 1 mm. thick. Thereafter, the electric resistance of the sheet was measured by the same method as in Example 1. The results are shown in the following Table 6.

TABLE 6 Surface Resistivity (9) Volume Resistivity (SE-cm.)

Antistatic Agent No.

Example 4 1 part of Antistatic Agent No. 7 was blended with 100 parts of polypropylene pellets as in the case of Example 1 and then the mixture was extruded in a sheet form of 1 mm. thick at a die temperature of 220 C. Thereafter, the electric resistance and the electrostatic voltage of the sheet were measured by the same method as that of Example 1. The results are shown in Table 7.

1 part of dibutyl tin maleate as a stabilizer was incorporated by means of a roll mill at a temperature of 120 C. into 100 parts of copolymer substance composed of vinyl chloride and 15% vinyl acetate, from which two pieces of test sample were prepared. The one was used for Blank Test and the other was mixed with 1 part of Antistatic Agent No. 3 when it was being incorporated in the roll mill. The respective test sample was extruded in a sheet form of 1 mm. thick as in the case of Example 1. Then the electrostatic voltage by friction of the sheet was measured like Example 1. The results are shown in the following Table 8.

parts of nylon chip and 2 parts of Antistatic Agent No. 7 were mixed like Example 1. This blended nylon chip was melted and spun by use of a spinning machine at a nozzle temperature of 260 C. and then stretched four times by length. The filament of 300 denier thus obtained was aged at a constant temperature of 20 C. and at a relative humidity of 65%, after which the electric resistance of the filament was measured at the same conditions of temperature and humidity. The results are shown in Table 9 below.

TABLE 9 Antistatic Agent No.: Resistivity (t2) 7 82x10 Blank test 3.8 1O

Example 7 The procedure of Example 6 was repeated with the exception that 2 parts of Antistatic Agent No. 7 were incorporated into 100 parts of polyethylene-glycol terephthalate at a nozzle temperature of 270 C. The test results are shown in Table 10 below.

TABLE 10 Antistatic Agent No.: Resistivity (f2) 7 4.8 10 Blank test 4.5 10

Example 8 1 part of a metal salt of amphoteric surface activator synthesized from 1-aminoethyl-2-alkylimidazoline and monochloroacetic acid was mixed with 100 parts of high density polyethylene pellet as in Example 1 and then this mixture was extruded in a sheet form of 1 mm. thick. Thereafter, the electric resistance of the sheet was measured by the same method as that of Example 1. The results are shown in Table 11 below.

NCH2 R-G /N CH2 M IIO CHzCHzOOHgCOO OHiC O 0 Antistatic Surface Volume Agent No. R M Resistivity Resistivity (Kl-cm.)

3.5X10 5.7)(10 6.2Xl0 4.1)(10 4.5X10l 5.8)(10 28 6.8X10 1.7)(10 Blank 'lest-. 8.l 10 1.8)(10 Although the present invention has been described in conjunction with preferred embodiments, it is to be understood that modifications and variations may be resorted to without departing from the spirit and scope of the invention, as those skilled in the art will readily understand. Such modifications and variations are considered to be within the purview and scope of the invention and appended claims.

What is claimed is:

1. A method of suppressing electrostatic charges in synthetic polymers, copolymers and polycondensates and/ or fibers susceptible to accumulating static charges and selected from the group consisting of polyethylenes, polyvinylchloride, polymethacrylates, polyamides, polyethyleneglycol terephthalates, polypropylene, polystyrene and copolymers of vinyl chloride and vinyl acetate by incorporating therein 0.05 to 5.0% by weight of a substance having the following structural formula:

wherein R is a radical selected from the group consisting of alkyl radicals containing 7 to 21 carbon atoms; X is a substance selected from a group consisting of wherein n is an integer of from 1 to 6, m is an integer of from 1 to 7, Y is an alkylene radical containing 2 to 6 carbon atoms, and R and R are selected from a group consisting of H, alkyl radicals containing 1 to carbon atoms, hydroxyalkyl radicals, alkylaryl radicals,

M is selected from a group consisting of H, Mg, Ca, Cd, Sn, Ba, Pb, Al, Fe, Co, Ni, Cu, Zn and Mn, said H not being used in the state of H alone; and x and y are numbers which are determined by valency of said M and number of anions in of the formula respectively.

8 2. A method according to claim 1, in which the compound represented by X is -(CH CH O) -H.

3. A method according to claim 1, in which the compound represented by X is 4. A method according to claim 1, in which the compound represented by X is (CH CH O),,CH COO.

S. A method according to claim 1, in which the compound represented by X is 6. A method according to claim 1, in which the compound represented by X is 7. A method as described in claim 2 in which the synthetic polymer is low-density polyethylene.

8. A method as described in claim 6 in which the synthetic polymer is low-density polyethylene.

9. A method as described in claim 2 in which the synthetic polymer is polystyrene.

10. A method as described in claim 2 in which the synthetic polymer is polypropylene.

11. A method as described in claim 2 in which the synthetic polymer is copolymer of vinyl chloride and vinyl acetate.

12. A method as described in claim 2 in which the synthetic fiber is polyamide.

13. A method as described in claim 2 in which the synthetic fiber is polyethylene glycol terephthalic acid ester.

14. A method as described in claim 2 in which the synthetic resin is high-density polyethylene.

References Cited by the Examiner UNITED STATES PATENTS 2,528,380 10/1948 Mannheimer et al. 260309.6 2,781,349 2/1957 Mannheimer et al. 260309.6 2,781,357 2/1957 Mannheimer et al. 260-3096 WILLIAM H. SHORT, Primary Examiner.

SAMUEL H. BLECH, Examiner.

R. LYON, Assistant Examiner. 

1. A METHOD OF SUPPRESSING ELECTROSTATIC CHARGES IN SYNTHETIC POLYMERS, COPOLYMERS AND POLYCONDENSATES AND/ OR FIBERS SUSCEPTIBLE TO ACCUMULATING STATIC CHARGES AND SELECTED FROM THE GROUP CONSISTING OF POLYETHYLENES, POLYVINYLCHLORIDE, POLYMETHACRYLATES, POLYAMIDES, POLYETHYLENEGLYCOL TEREPHTHALATES, POLYPROPYLENE, POLYSTYRENE AND COPOLYMERS OF VINYL CHLORIDE AND VINYL ACETATE BY INCORPORATING THEREIN 0.05 TO 5.0% BY WEIGHT OF A SUBSTANCE HAVING THE FOLLOWING STRUCTURAL FORMULA: 